1. Field of the Invention
This invention relates to aqueous mixtures suitable for use as release agents and to their use in the production of hotmelt adhesives, more especially pressure-sensitive hotmelt adhesives.
2. Description of Related Art
Hotmelt adhesives, also known in brief as hotmelts, are used for bonding in various fields. Among hotmelt adhesives, those of the pressure-sensitive, i.e. permanently tacky, type occupy a special position. Due to this special ability to remain tacky, even at room temperature, they give rise to particular problems when it comes to their application.
A special technique has been developed for the production and processing of hotmelt adhesives (cf. "Seifen, Oele, Fette, Wachse" (1976), pages 279 to 282). After the raw materials required for the adhesive have been melted, the adhesive is granulated. For example, a hotmelt may be applied in the form of strips to a cooled steel belt optionally covered by a film of water. After the adhesive has cooled sufficiently, it is size-reduced in a cutter unit. This operation may be carried out in the presence of aqueous release agents, such as solutions of anion-active wetting agents or water-soluble soaps. It may also be necessary to powder the granules with talcum or the like.
Hitherto, it has not been possible to granulate or pelletize the pressure-sensitive permanently tacky hotmelt adhesives which have been successfully used for numerous applications. Although attempts have been made to coat permanently tacky hotmelt adhesives with a layer of a temporarily tacky adhesive and, in this way, to obtain pellet-like forms after size-reduction, elaborate machinery is required for this purpose. In practice, therefore, the permanently tacky hotmelt adhesives are still packed in cartons coated with release agents and left therein until they are actually used, i.e. melted.